Frostið á rúðunni er svo mikið að ég þarf að skafa það af áður en ég fer.

Frost means frost, and frostið means the frost. The ending -ið is the attached definite article, which Icelandic often adds directly to the noun instead of using a separate word like English the.

Here, frostið is neuter singular nominative: the frost.

Because á can take different cases depending on meaning. When it means on in a location sense, it usually takes the dative.

So:

• rúðan = the window/pane in nominative
• rúðunni = the window/pane in dative

Since the frost is located on the pane, Icelandic uses á rúðunni.

More exactly, rúða usually means pane or window glass. That makes it a very natural word here, because frost forms on the glass itself.

If you said gluggi, that usually means window more generally, as the whole window opening/frame.

Because the adjective has to agree with frostið, which is a neuter singular noun. The adjective mikill changes form:

• mikill = masculine
• mikil = feminine
• mikið = neuter

So frostið er svo mikið uses the neuter form mikið.

This is a very common pattern meaning so much ... that.

So:

• svo mikið = so much
• að = that

Together, frostið er svo mikið að... means the frost is so much/heavy that...

Because þurfa normally takes að + infinitive. So:

• ég þarf að fara = I need to go
• ég þarf að skafa = I need to scrape

English uses to, and Icelandic often uses að in the same kind of structure.

Skafa means to scrape, and af adds the sense of off. So skafa af means scrape off.

It works a lot like an English verb + particle combination:

• skafa það af = scrape it off

With short object pronouns like það, Icelandic commonly places the pronoun before the particle:

• skafa það af
• taka það upp
• slökkva það ekki is not a good example because that uses a different structure, but the same idea of pronoun placement often appears with particles

So skafa það af is the natural order for scrape it off.

It refers back to frostið. Since frost is a neuter noun, the pronoun is það.

In this sentence, það is the direct object of skafa: scrape it off.

Áður en means before when it introduces a clause.

So:

• áður en ég fer = before I go / before I leave

It is a fixed expression, and very common in Icelandic.

Because these are subordinate clauses. Icelandic usually has verb-second word order in main clauses, but after conjunctions like að and en, the subject normally comes before the verb.

So:

• ég þarf... = normal subordinate-clause order here
• ég fer = also normal after áður en

That is why you do not get að þarf ég or en fer ég here.

Because Icelandic often uses the present tense for future meaning when the context already makes the time clear. After a time expression like áður en, this is especially common.

So áður en ég fer literally looks like before I go, but it naturally means before I leave in the future context of the sentence.